Photoelectric sizing mechanism



Feb. 4, 1947.

s. c. HURLEY, JR

PHOTOELECTRIQ SIZING MECHANISM s Sheets-Sheet 1 mm Samugl C. Hurle: ,Jr.

Filed March 22, 1943 Feb. 4, 1947. 5 HURLEY, JR 2,415,174 IPHOTOELECTRIC SIZING MECHANISM Filed March 22, 1943 v 3 Sheets-Sheet 2Samuel C. Hurley, Jr.

Feb. 4, 1947. s. c. HURLEY, JR

PHOTOELECTRIC SIZING MECHANISM 3 Sheets-Sheet 3 Filed March 22, 1943llAAA Gum/Mg ted e d Edd? 2,.dl5,1?d

PRGTOELECTRIC SIZING MECHANISM Samuel E. Hurley, Jim, Danville, 111.

Application March 22, 1943, Serial No. 480,026

(Cl. 209--8Z) 9 illaims. i

This invention relates to photoelectric sizing mechanism and moreparticularly to a device which will select articles of a predeterminedsize and reject articles or specimens which are a predetermined amountover or under the desired size. The mechanism causing acceptance orrejection of the specimen is controlled by the passage of the articlethrough a beam of light and no stationary support or rest is requiredfor the specimen being tested. The testing operation may be performedwhile the specimen is in motion.

In general, the device includes a plurality of phototube bridges, oneresponsive to the conditions of light and shadow due to the one edge ofthe article, and another responsive to the conditions of light andshadow due to the other edge of the specimen being tested. The bridgeseach include a pair of phototubes, each tube forming an arm of thebridge, and if the specimen is of the correct dimension one of thephototubes of each bridge will be in shadow while the other phototube ofeach bridge is in light. The bridges are so connected as to beunbalanced under these conditions and a selecting mechanism is actuated.If either of the bridges is in balance, that is to say, if thephototubes of either bridge are both in light or both in shadow, areject mechanism is actuated to reject the article or at least aselecting mechanism is not actuated. The entire device is preferably soarranged and connected that it is necessary to positively actuate aselecting mechanism in order to accept the specimen so that failure ofany portion of the device causes the specimens to be rejected.

An object of the present invention is, therefore, to provide an improvedsizing mechanism which may operate upon specimens in motion withoutphysical contact between the testing instrumentalities and the article.

Another object of the invention is to provide a phototube sizing deviceincluding a plurality of phototube bridges all of which must be inunbalanced condition in order to select the specimen.

Another object of the invention is to provide an improved photoelectricsizing device controlled by passage of an article to be sized through abeam of light and which requires positive actuation of a selectingmechanism in order to accept the specimen being sized so that failure ofcomponent parts of the device cause rejection rather than selection ofthe specimen.

Another object of the invention is to provide a photoelectric sizingmechanism in which a lens system and a plurality of concave mirrors areemployed to magnify the departure of an article from a predeterminedstandard so as to enable the device to work within closed tolerances.

A further object of the invention is to provide an improved sizingdevice having a. plurality of phototube bridges in which the relativeposition of the various phototubes and otherelements of the device maybe varied to vary the tolerance permitted by the bridge before acceptingan article being tested. 7 I

Other objects and advantages of the illVEZl? tion will appear in thefollowing description of the preferred embodiments of the inventionshown in the attached drawings, in which Fig. 1 is a schematic viewshowing the mechanical arrangement of the sizing device of the presentinvention and an electric circuit associated therewith;

Fig. 2 is a diagrammatic plan view of the me chanical portion of thedevice;

Fig. 3 is a simplified schematic diagram of the circuits of Fig. 1; and

Fig. 4 is a view similar to 3 showing a modified circuit.

Referring to the drawings, the device illustrated in Figs. 1 and 2includes a source of light iii shown as an electric incandescent lamp,although any other suitable source of concentrated light can beemployed. The lamp it has its filament positioned substantially in theoptical axis of a pair of condenser lenses H for concentrating the lightof the source I0 upon an article it being passed through the beam oflight from the condenser lenses H. A projecting lens assembly i3 ismounted so as to have its optical axis in alignment with the opticalaxis oithe condensing lenses II, and is positioned upon the oppositeside of the test zone through which the article 52 is passed. Theprojecting lens assembly i3 preferably projects a sharply defined shadowof the article being tested upon a plurality of convex mirrors l4 and isshown as being cylindrical mirrors, although other types of convexmirrors, including a spherical mirror, may be employed. That is, theobject being tested and the mirrors it and 16 are preferably positionedat the conjugate foci of the lens assembly. The mirrors M and I6 arepositioned so-thatfor a perfect article the edge of the shadow cast bythe upper edge of the article l2 in Fig. 1 will be approximatelycentered in a vertical direction upon the mirror !6 when the edge of theshadow cast by the lower edge of the article 12 is approximately 3centered in a vertical direction upon the mirror- I4. A cylindricalarticle 12 is shown by way of example, but other shaped articles may betestedit correctly passed through the light beam between the condenserlenses and the projecting lens assembly I3.

Phototubes I1 and I8 are positioned to receive light from the mirror l4and phototubes l9 and 20 are positioned to receive light from the mirrorl6, a light baffle 22 being positioned between the mirrors l4 and I6 toprevent light from mirror I4 from reaching phototubes i9 and. 20 andlight from mirror l6 from reaching phctotube H. The phototubes andmirrors are so adjusted that the upper edge of an article which iswithin the tolerance range and in test position inthe beam of lightbetween the lenses ii and l3 will cause phototube l9 to be in shadow andphototube 20 to be in light while at the same time the lower edge of thearticle will cause'phototube I8 to be in shadow and phototube H to be inlight. This condition is necessary for actuation of the selectingmechanism to accept an article.

The electric circuit for the phototubes and control apparatus is'mostclearly shown in Fig. 3 and as shown therein the phototubes l1 and I8are connected in series across a source of D.-C. potential. Resistors 23and 24 are also connected across said source, these resistors beingsubstantially equal, and the midpoint of the resistors is a, controltube 21, preferably of the pentode' type, is connected to the point 28between the phototubes l1 and I8. The point 28 is normally maintained atground potential when the voltage drops through the phototubes l1 and I8are substantially equal, by means of a resistor 29 having a relativelyhigh resistance connected to ground at-3I. It will be apparent that thepoint 28 and the control grid of the tube 21 remain at substantiallyground potential when the phototubes l1 and I8 are non-conducting orwhenboth are rendered conducting to approximately the same extent byimpingement of light thereon. Thus, the resistors 23, 24 and thephototubes ll and I8 .form the four arms of a bridge with the resistors29 connected across the bridge at the junction of the arms remote fromthe junctures connected to the source of D.-C. potential.

The tube 21 may have its operating voltages obtained from a plurality ofvoltage dividing \resistors 32, 33, 34 and 35 connected between thepositive terminal 31 of a separate source of D.-C. potential and groundat 3|, the negative terminal of the source of D.-C. potential beingconnected to ground at 38. The resistors 32 to 35, inclusive, provideproper operating voltages for the tube 21, the anode of this tube beingfurnished with a relatively high positive potential through a loadresistor 39. The screen grid of the tube 21 is connected to a point ofsomewhat lower positive potential between the resistors 33 and 34. Thecathode of the tube 21 may be connected to a variable slider 4| engagingthe resistor 35 at a point which is at a positive potential above groundso as to apply an effective negative. bias to the control grid of thetube 21 with respect to the cathode thereof. The amount of bias thusplaced on the control grid is preferably a relatively low negativepotential so that considerable current flows in the anode circuit of thetube 21. It will be apparent that this bias is not disturbed as long asphototubes l1 and 18 are nonconducting or conducting to substantiallyequal extentsbut that the bias on the control grid connected to groundat 26. The control grid of of the tube 21 will be changed if one of thephototubes or I8 is sub-nected to light while the other remains inshadow.

The control tube 21 in conjunction with a similar control tube 42 isemployed-to control the action of the power tube 43 which is preferablyof the gas filled grid controlled arc discharge type. The control tube42 is connected with respect to phototubes i9 and 2D in a manner exactlysimilar to the connection of the control tube 21 with respect to thephototubes [Band II. Thus, the phototubes I9 and 26 are connected inseries across the resistors 23 and 24 so as to also form a bridgetherewith. The control grid of the tube 42 is connected to a point 44between the phototubes l9 and 20 and to ground through a resistor 46having relatively high resistance so that the normal potential of thecontrol' grid of the tube 42 is substantially that of ground. Aplurality of voltage dividing resistors 41, 48, 49 and 5!] supply propervoltages to the electrodes of the tube 42 in a manner entirely similarto the voltage supply of the tube 21, the anode of the tube 42 beingconnected to a relatively high positive potential through the loadresistor 52.

The tube 43 may have its cathode connected to a relatively lowpositivepotential maintained by the voltage dividing resistors 53 and54-connected between the positive terminal 31- of a D.-C. voltage sourceand ground. The potential of the cathode of the tube 43 is thusmaintained positive with respect to the control electrode 56 of the tube43 and also with respect to the shield electrode 51 of this tube. Thusthe control electrode 58 and the shield electrode 51 of the tube 43normally have sufficient negative bias to maintain the tube 43 innon-conducting condition when the tube is not ionized. A relay coil 58and a mechanically operated switch 59 are connected in series, oneterminal of this circuit being connected to the positive terminal 31 ofthe source of D.-C. potential and the other terminal being connected tothe anode of the tube 43. Thus,

when the tube 43 is in non-conducting condition or switch 59 is open,the coil- 58 is not energized.

but upon closing ofthe switch 59 and rendering the tube 43 conducting,the relay coil 58 is energized to attract an armature 61 opening acircult through normally closed contact 63 and closing a circuit throughnormally open contact 64. It has been found that the control electrodeand shield electrode of certain types of gasfilled tubes may be employedto substantially independently control the ionization of the tube. Thatis to say, a sufliciently negative bias on either one of theseelectrodes will prevent ionization irrespective of 6 Whether the otherelectrode has a positive potential applied thereto with respect to theoathode.

A source of alternating current power shown as an alternating currentline 66 hasone side connected to the armature 6| and the other side to aterminal of another mechanically operated switch 61 so that closing ofthe mechanicalswitch 6'! completes a circuit through one or the other ofsolenoid operated valves 68 and '69 depending upon which contact 63 or64 is in engagement with the armature 6| of the relay. The solenoidvalves 69 and 68 control selecting and rejecting mechanismsrespectively. Thus, referring to Fig. 1, the solenoid'valves 68 and 69may be connected to a, source of fluid pressure (not shown) through apipe II and maybe provided with discharge pipes 12 and 13, respectively.If the article to be tested is moved. through the light beam in thedirection indicated by the arrow is in Fig. 1, immediately after it hasbeen tested a blast of air or other fluid from the pipe 72 may beemployed to propel the article i2 into a select receptacle (not shown),or a blast of fluid from the pipe is may be employed to propel thearticle into a reject receptacle (not shown) depending upon the positionof the relay armature ti.

The mechanical switches 5d and ill may be operated by cams M and it,respectively, driven in synchronism, as indicated by the dotted lineconnecting the two cams, so that the switch 59 is closed when thearticle reaches the test position in the light beam between thecondenser l lenses It and the projecting lens it and the switch it isclosed thereafter.

Preferably the switch 5% is closed just before the article reaches thedesired test position and the switch t? is closed just after the articlereaches the test position so that the circuit through the tube id isconditioned for operation just prior to the articlereaching the testposition in the light beam. The relay coil 58 is not energized unlessthe article is within the predetermined tolerance range, but if said.article is within the predetermined tolerance range the solenoid coil 59is energized to attract the armature El and condition the circuit foracceptance of the article by closure of the contact 5t. Subsequentclosure of the circuit through the switch til then operates the solenoidvalve 63 to select the article. If the article is not within thetolerance range the relay coil 58 is not energized upon closure ofswitch 59 since the tube 63 has not been rendered conducting andsubsequent closure of the switch bl operates the solenoid valve (it toreject the article. It will be noted that the article is always rejectedunless the relay coil 58 is energized requiring that both the tube isand relay positively function in order to accept the article. Continuedrotation of the cams it and it causes opening of the circuit through theswitches to deionize the tube to and open the circuits through eitherthe solenoid valve 68 or valve 6% to condition the device for subsequenttest operation.

The bias upon the control grids of the control tubes 2? and ift isnormally held at a relatively low negative potential by the connectionsshown so that a substantial current flows in the anode circuit of thesetubes when the bridges including the phototubes ll and t8 and thephototubes l9 and 2d are in balance. This current flowing through theload resistors 3d and 52 of the tubes 2i? and d2, respectively, maintainthe control electrode stand shield electrode 57 of tube at at a negativepotential with respect to the cathode of'the tube it to preventionization of this tube even when the mechanical switch 59 is closed.Thus when both bridge circuits are balanced, closure of mechanicalswitch 67 will cause operation of the reject solenoid switch 69.

The article to be tested may be passed through the beam of light betweenthe condenser lenses H and the projecting lens it in the direction shownby the arrow l t in Fig. 1. Before the article enters the beam all ofthe phototubes ll to 29, inclusive, are subjected to light from thelight source reflected from the mirrors i l and It and the two phototubebridges are in balance. However, the mechanical switch ill] is open sothat there is no operation of the selecting or rejust at this time orshortly potential.

As the article enters the light beam the leading edge of the articlereaches a point in which the phototube I1 is placed in shadow while thephototube 18 remains in the light. Even if the mechanical switch 59 wereclosed at this point no ionization of the tube it would take place asplacing the phototube l? in shadow so that the control grid of tube 27is driven in a positive direction increases the nega tive bias on thecontrol grid to of the tube at. As the article is progressed furtherinto the light beam both phototubes l1 and 3 are placed in shadow sothat the bridge containing these tubes again returns to balance, stillretaining the bias on the control grid of the tube 43 at a negativeDuring this time the phototubes It and 20 remain in light so that thebridge containing these tubes remains balanced, thus maintaining thenegative potential upon the shield electrode 57 of the tube is.

As the article progresses through the light beam it reaches a point atwhich the phototube i9 is placed in shadow while the phototube 'Edremains in the light. This unbalances the bridge containing thephototubes l9 and 20 to drive the control grid of the tube Min anegative direction to decrease the anode current through the tube it.This reduces the drop through the load resistor 52 of this tube andallows the shield grid 5? of the tube W to become positive or at leastbe carried in a positive direction with respect to the cathode of thistube so that the control grid 5% of the tube is conditioned for causingionization of the tube.

If the article is larger than the predetermined size both phototubes l7and It remain in shadow so that this bridge remains balanced and thecontrol grid 56 of the tube d3 remains negative. At this time themechanical switch 59 has been closed but the relay coil 58 is notenergized because the tube 63 remains non-conducting. Shortly thereafterthe mechanical switch 67 is closed and reject solenoid valve is operatedto reject the article as hereinafter described.

7 If the article is within the predetermine tolerance range thephototube I8 is placed in shadow while phototube I1 is still in thelight and it will be remembered that the article is in such a positionthat phototube l 9 is placed in shadow while phototube 20 is in' thelight. This unbalances both phototube bridges so that both the controlelectrode 56 of the tube 43 and the shield electrode 5! are carried in apositive direction. As mechanical switch 5% is closed, the tube 33ionizes, the. relay coil 58 is energized, and upon closure of mechanicalswitch 61 the solenoid valve 68 is energized to accept the article.

If, however, the article tubes IT and it are in the light when theleading edge of the article reaches a position such that phototube I9 isin shadow, and phototube ml is in light so that the control electrode 55of the tube 43 is maintained negative when the shield elecjecting mochatrode 51 thereof is carried in a positive direction.

The tube 43 does not ionize even though the switch 59 is closed and uponclosure of the switch 57 the reject solenoid valve 69 is operated.

It will be apparent from the above description of operation, that theonly condition under which the accept solenoid valve 68 can be operatedis. that the article be of the correct size to place phototube I9 inshadow when phototube 21! is in light while at the same time placingphototube Id in shadow while phototube I! remain; in the light. Thismeans that the article must be withis too small,'both photoin thepredetermined tolerances and occupy a predetermined position in thelight beam. Thus, the articles can be moved through the light beam ineither direction alon a line perpendicular to the axis of the mirrors I4and I5 in timed relation with properly synchronized mechanical switchesin the control circuits and the selecting mechanism will not operate toaccept the article unless the above conditions are fulfilled. After thoperation of the selecting mechanism to either accept or reject thearticle, the switch 81 is opened to deenergize the solenoid-valve 68 or89 operated to either select or reject the article and the switch 59 isopened to deionize the tube 43.

While the switches 59 and 81 must be operated in timed relationship withthe passage of articles through the beam of light, their adjustment isnot extremely critical. Thus, the switch 59 must be closed while theswitch 61 is open at least the switch 51 must not close before theswitch 59 closes. It-is merely necessary that the switch 59 opensometime between test operations in order to deionize the tube 43. Thisswitch can be again closed at any time prior to closing of the switch 61but must be closed at the time the article reaches the test position inthe light beam. The switch 61 must not close before the article reachesthe may remain closed for a considerable portion of the test cycle.

The device of Fig. 4 is entirely similar to the device of Fig. 3 exceptthat another gas filled tube Bi and relays 82 and 83 are substituted forthe mechanical switches 59 and 6T| of Fig. 3 in order to make theoperation of the selecting mechanism entirely dependent upon the passageof the article through the light beam so as to avoid the necessity ofhaving a mechanically operated switch synchronized with passage of thearticle through th light beam. Otherwise the same reference numerals areemployed for corresponding parts upon Figs. 3 and 4.

The control electrode 84 of the tube 8| is connected in parallel withthe control electrode 56 of tube 43 but has its shield electrode 88connected to the cathode so that the tube 8| ionizes whenever thecontrol electrode 84 is carried in a positive direction. Thus, unbalanceof the bridge including the phototubes I1 and I8 by placing phototubeiii in shadow and phototube l1 in light, causes'ionization of tube 8| asabove described when its anode circuit is closed, and this can onlyhappen when the article is substantially centrally positioned in thelight beam and the lower edge of the article occupies a position wherephototube i1 is in light and phototube I8 is in shadow. At this timephototubes l9 and 28 are determining the position of the upper edge ofthe article. Whentube 8| is thus ionized, as above described, the coil88 of relay 82 is energized to attract armature 89 to close a circuitthrough contact 9| of relay 82, and one of the contacts 63 and 64associated with relay coil 58, and through one of the solenoid valves 68or 69 to operate either the selecting mechanism to either accept orreject the article.

If the article is within the tolerange range, the

size or oversize the bridge including phototubes l9 and is in balance atthe time tube 8| ionizes so that tube 43 does not ionize and a circuitis completed through the reject solenoid operated valve 69 to reject thearticle. Operation of relay 82 due to ionization of tube 8| also closesa circuit through contact 93 of relay 82 and the operating coil 94 ofrelay 95 which causes opening of the anode circuits of the tubes 43 and8| at norerances can be set within desired limits.

mally closed contact 980i relay 95. This causes deionization of tubes 43and 8| to condition the same for a subsequent operation. Relay ispreferably of the delayed action type so that the tubes 43 and 8| arenot deionized until after the selecting mechanism has had an opportunityto operate.

It will be apparent that tube 8| will only ionize and becomeconducting'when the article is in test position in the light beam andthat the ionization of tube 8| completely controls the time of operationof the selecting or rejecting mechanism.

Thus, mere passage of the articles through the light beam not only teststhe article for correct size, but also initiates the operation of theselecting mechanism. It will be further apparent that in the device ofFig. 4 the tube 21 and the circuit associated therewith must havesufiicient power to drive the control grids of both tubes 43 and 8| in apositive direction irrespective of electron flow to these controlelectrodes when the control electrodes are carried in a positivedirection. In

some instances, therefore, it may be necessary to employ a separateamplifying tube .such as 2 for each of the control electrodes of thetubes 43" 28 is essentially similar to the bridge including the tubes i1and I8 and is only unbalanced in the correct manner'to carry theelectrode of a gas filled tube in the positive direction when thearticle is in thetest position in the light beam, it is also entirelypossible to control the tube 8| from the bridge including the phototubesl1 and l8. a

It will thus be seen that the present invention provides a sizing orsize determining device which does not require that an article undertest be held in a stationary predetermined position. Instead merepassage of an article through a light beam causes acceptance orrejection of the article. Any

known or suitable conveying or article moving means such as a belt orchain can be employed to move the articles through the beam and anysuitable accepting and rejecting mechanism can be actuated by the photocell bridges for directing the tested articles to receivers as theyleave the test zone. extremely accurate and the over or under tolbeapparent that it is unnecessary for both edges of the article beingmeasured to be positioned in the same light beam as separate beams canbe employed for opposite edges of large articles and furthermore morethan one dimension of an article can be simultaneously measured byemploying The test for correct size can be made It ,will

a a larger number of phototube circuits and if necessary a plurality oflight beams.

While I have disclosed the preferred embodi ments of my invention, it isunderstood that the details thereof may be varied within the scope ofthe following claims.

I claim as my invention:

1. In a phototube sizing device, a light sourceand an optical systemproviding at least one light beam, means for determining whether adimension of said article intercepting a portion of said beamcorresponds to a predetermined dimen'sion comprising a first phototubecircuit responsive to light passing one edge of said article fordetermining when said edge occupies a predetermined position and asecond phototube circuit responsive to light passing another edge ofsaid article for simultaneously determining whether said other edgeoccupies another predetermined position, each of said phototube circuitsincluding a pair of phototubes, one of said phototubes of each circuitbeing positioned to receive light passing its corresponding edge and theother phototube of each circuit being positioned to be placed in shadowby said corresponding edge when said corresponding edge occupies itspredetermined position, each of said photutube circuits being connectedto form a bridge so that the bridge of each circuit is substantially inbalance when both phototubes thereof receive light or are in shadow andis unbalanced when one phototube thereof receives light and the otherphototube thereof is in shadow, and selecting means controlled by bothsaid phototube circuits for accepting said article when both of saidbridges are simultaneously unbalanced and rejecting said article whenone of said bridges is unbalanced in one direction only and the other ofsaid bridges is in balance.

2. In a phototube sizing device, a light source and an optical systemproviding at least one light beam, means for determining whether adimension of said article intercepting a portion of said beamcorresponds toa predetermined dimension comprising a first phototubecircuit responsive to light passing one edge of said article fordetermining when said edge occupies a predetermined.

position and a, second phototube circuit responsive to light passinganother edge of said article for simultaneously determining whether saidothor edge occupies another predetermined position, and selecting meanscontrolled by both said phototube circuits for accepting said articlewhen both said edges simultaneously occupy their correspondingpredetermined positions, said selecting means including a control tubeof the arc discharge type having a cathode and two control electrodes,electrical circuits and a source of voltage for maintaining each of saidelectrodes at a voltage with respect to said cathode preventingionization of said control tube, each of said phototube circuits beingconnected to one of said control electrodes to carry the voltage thereofin a positive direction when the corresponding edge of said articleoccupies its predetermined position, whereby said control tube ionizeswhen said edges simultaneously occupy their predetermined positionsonly, and selecting means responsive to ionization of said control tubefor accepting said article.-

. 3. In a phototube sizing device, a light source and an optical systemproviding at least one light beam, means for determining whether adimension of said article intercepting a portion of said beamcorresponds to a predetermined dimension asserts comprising a firstphototube circuit responsive to light passing one edge of said articlefor determining when said edge occupies a, predetermined position and asecond phototube circuit responsive to light passing another edge ofsaid article for simultaneously determining whether said other edgeoccupies another predetermined position,

and selecting means controlled by both said phototube circuits foraccepting said article when both said edges simultaneously occupy theircorresponding predetermined positions, said selecting means including acontrol tube of the grid controlled arc discharge type having a cathode,a control electrode and a shield electrode, electrical circuits and asource of voltage for maintaining each of said electrodes at a voltagewith respect to said cathode preventing ionization of said control tube,one of said phototube circuits being connected to said control electrodeto carry the voltage thereof in a, positive direction when itscorresponding edge is in said predetermined position, and the other ofsaid phototube circuits being connected to said shield electrode tocarry the voltage thereof in a positive direction when its correspondingedge occupies its predetermined position, whereby said tube ionizes whensaid edges simultaneously occupy their predetermined positions only, andmeans responsive to ionization of said control tube for accepting saidarticle.

4. In a phototube sizing device, a light source and an optical systemproviding at least one light beam, means for determining whether a,dimension of said article intercepting a portion of said beamcorresponds to a predetermined dimension comprising a first phototubecircuit responsive to light passing one edge of said article fordetermining when said edge occupies a predetermined position and asecond phototube circuit responsive to light passing another edge ofsaid article for simultaneously determining whether said other edgeoccupies another predetermined position, and selecting means controlledby both said phototube circuits for accepting said article when bothsaid edges simultaneously occupy their corresponding predeterminedpositions, said selecting means including a control tube of the arcdischarge type having a cathode and two control electrodes, electricalcircuits and a source of voltage for maintaining each of said electrodesat a voltage with respect to said cathode preventing ionization of saidcontrol tube, each of said phototube circuits being connected to one ofsaid control electrodes to carry the voltage thereof in a positivedirection when the corresponding edge of said article occupies itspredetermined position, whereby said control tube ionizes when saidedges simultaneously occupy their predetermined positions only, andselecting means responsive to ionization of said control tube foraccepting said article and rejecting said article when said control tubefails to ionize, said last named means including a second control tuberesponsive to one of said phototube circuits for sion of said articleinterceptin a portion of saidbeam corresponds to a predetermineddimension comprising a first phototube circuit responsive to lightpassing one edge of said article for determining-when said edge occupiesa predetermined position and a second phototube circuit position, andselecting means controlled by both said phototube circuits for acceptingsaid article when both said edges simultaneously occupy theircorresponding predetermined positions, said selecting means including acontrol tube of the arc discharge type having a cathode and twocontrolelectrodes, electrical circuits and a source of voltage for maintainingeach of said electrodes at a voltage with respect to said cathode pre-;venting ionization of said control tube, each of said phototube circuitsbeing connected to one of said control electrode: to carry the voltagethereof in a positive direction when the corresponding edge of saidarticle occupies its predetermined position, whereby said control tubeionizes when said edges simultaneously occupy their predeterminedpositions only, and selecting means responsive to ionization of saidcontrol tube for accepting said article and rejecting said article whensaid control tub fails to ionize, said last named means including asecond control tube of the arc discharge type having a control electrodeconnected to one of said phototube circuits to cause ionization of saidsecond control tube when one of said edges occupies its predeterminedposition irrespective of the position of the other of said edges, meansresponsive to ioniza-- tion of said second control tube for initiatingoperation of said selecting means and for thereafter causingdeionization of both said control tubes.

6. In a phototube sizing device, a light source and an optical systemproviding at least one light beam, means for determining whether adimension of said article intercepting a portion of said beamcorresponds to a predetermined dimension comprising a first,phototubecircuit responsive to light passing one edge of said article fordetermining when said edge occupies a predetermined position and asecond phototube circuit responsive to light passing another edge ofsaid article for simultaneouslydetermining whether said other edgeoccupies another predetermined position, each of said phototube circuitsincluding a pair of phototubes, one of said phototubes of each circuitbeing positioned'to receive light passing its corresponding edge and theother phototube of each circuit being positioned to be.

placed in shadow by said corresponding edge when said corresponding edgeoccupies its predetermined position, each of said phototube circuitsbeing connected to form a bridge so that the bridgeof each circuit issubstantially in balance when both phototubes thereof receive.

light or are in shadow and is unbalanced when one phototube thereofreceives light and the other phototube thereof is in shadow andselecting means controlled by both said phototube circuits for acceptingsaid article when both said bridges are simultaneously unbalanced, saiddevice having a convex mirror individual to each of said phototubecircuits and a projecting lens for focusin the shadow of thecorresponding edge of said article upon the corresponding mirror, thephototubes of each circuit being positioned to I receive reflected lightor shadow from said mirror corresponding to its circuit.

7. In a phototube sizing device, a light source mension comprising afirst phototube circuit responsive to light passing one edge of saidarticle for determining when said edge occupies a predetermined positionand a second phototube circuit responsive to light passing another edgeof said article for simultaneously determining whether said other edgeoccupies another predetermined position, each of said phototube circuitsincluding a pair of phototubes, one of said phototubes of each circuitbeing positioned to receive light passing its corresponding edge and theother phototubeof each circuit being positioned to be placed in shadowby said corresponding edge when said corresponding edge occupies itspredetermined position, each of said phototube circuits being connectedto form a bridge so that the bridge of each circuit is substantially inbalance whenboth phototubes thereof and an optical system providing atleast one light beam, means for determining whether a dimension of saidarticle intercepting a portion of said beam corresponds to a.predetermined direceive light or are in shadow and is unbalanced whenone phototube thereof receives light and the other phototube thereof isin shadow, and

selecting means controlled by both said phototube circuits for acceptingsaid article when said bridges are simultaneously unbalanced, saiddevice having a convex mirror individualto each of said phototubecircuits and a projecting lens for focusing the shadow of thecorresponding edge of said article upon the corresponding mirror, thephototubes of each circuit being positioned to receive reflected lightor shadow from said mirror corresponding to its circuit.

8. In a photoelectric sizing device, a light source and an opticalsystem providing a light beam, means for determining the size of anarticle intercepting a portion of the light in said'beam including aphototube circuit responsive to light passing one edge of said articlefor determining the position of said-edge, said circuit including a pairof phototubes one of which receives light passing said edge and theother of which is placed in the shadow of said edge when said edge is ina predetermined position, a second phototube circuit responsive to lightpassing another edge of selecting said article when both said edges ofsaid article simultaneously occupy said predetermined positions andrejecting said article when one of said edges occupies its predeterminedposition and the other of said edges fails to occupy its predeterminedposition, said last named means-including a control tube of the aredischarge type having a control electrode and a shield electrode, one ofsaid circuits controlling the potential of one of said electrodes andthe other of said circuits controlling the potential of the other oisaid electrodes to provide for ionization of said tube when said edgessimultaneously occupy said predetermined positions only and meansresponsive to ionization of said control tube for accepting saidarticle.

9. In a phototube sizing device, a light source and an optical systemproviding at least one light beam, means for determining whether adimension of said article intercepting a portion of said beamcorresponds to a predetermined dimension, comprising a first phototubebridge circuit responsive to'light passing one edge of said article tionof the indicating means when one of said bridge circuits is balanced oris unbalanced in a 10 direction of potential opposite that for actuatingthe indicating means.

SAMUEL c. HURLEY. JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,237,811 Cockre11 Apr. 8, 19412,033,645 Parkhill Mar. 10, 1936 2,114,867 Wilson Apr.. 19, 19382,304,814 Glasser -Dec. 15, 1942 2,188,159 Rockwood -Jan. 23, 19402,085,671 Powers June: 29, 1937 1,873,315

Dreyer Aug. 23, 1932

